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20051031: McIDAS-related questions (cont.)



>From: address@hidden
>Organization: NMT
>Keywords: 200510212351.j9LNpI7s028398 McIDAS MYDATA

Hi Mekonnen,

re:
>(1) To give you more information related to my time-of-observation
>question. The datafiles I downloaded are GOES-10 imageries. I found the
>following information from the header information for each dataset (this
>is an example for one file):
>
>Image start time = 00:30:00 GMT
>Start Line = 4473
>Start Element = 18285
>Line resolution = 4
>Element resolution = 4
>
>And, my image size is 226 by 464 pixels.

OK.

>(2) I have downloaded about 3000 GOES-IR datafiles, each image is 226 by
>464 pixels. I extracted the brightness temperature in an ASCII format, and
>then using these ASCII files, I did my analysis in IDL . For example, one
>of my results that I created in IDL is the mean brightness temperature
>field.

OK.

>My question is how do I display this result (a 226 by 464 grid,
>obtained by averaging all the time series data for each grid)? If the data
>had a regular grid, then I could have displayed it either in IDL or
>ArcGIS.  However, the input GOES-IR data have irregular grids, and so I do
>not know how to display the resulting grid. Is my idea clear now perhaps?

I think I understand now.  You extract values (calibrated (e.g.,
temperature) or uncalibrated (e.g., brightness) from the GOES-10 images
you downloaded and are then using IDL to manipulate them.  Your
objective is then to put them back into a format where they can be
displayed by McIDAS or some other application (correct me if I am
wrong).  Here is the approach I would take:

- use MAKEAREA to put the values back into a McIDAS AREA file.  This
  gets you part of the way.
  
- add the navigation to the newly created AREA file.  If the navigation
  was simple, you could use MAKNAV to do this.  Unfortunately, MAKNAV
  does not support adding GVAR navigation to images.

The MAKNAV problem does have a solution albeit a manual one:

- extract the navigation from one of the images you downloaded and
  add it to the image.  This will be a manual step since it is
  not supported directly by MAKNAV.

In order to do this, you will need to learn about the structure of
McIDAS AREA files.  The first place to start is the McIDAS Programmer's
Reference Manual:

http://www.ssec.wisc.edu/mcidas/doc/prog_man/

>I'm sorry I sometimes have difficulty conveying my message in English.

What is your native language?

>What do you think?

I am thinking that I should modify MAKNAV and add an option that would
extract the navigation block from an existing AREA file and write it
to the AREA file designated by the user.  I will look into this, but
not until next week sometime.  In the meantime, I suggest that you
investigate the AREA file structure as described in the Programmer's
Reference Manual link above.

>Again thanks very much for your help,

Sorry I will be unable to get to the MAKNAV extension sooner...

Cheers,

Tom
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